Is that how you feel about your own mother, too? Now that you're here, she's trash?
My relationship with my mother is ethically different from my relationship with Mary. I owe my mother honor, support, care, respect. In comparison, I owe that other mother zip. Zero. Nothing.
You make an interesting arguement. A friend of mine is married to an incredible woman -- brilliant, beautiful, bilingual, and 20-some years yonger than my wife. If I start cultivating an affection towards my friend's wife that comes anywhere near the affection I have for my own wife, will God be pleased? Think about it ...
Knew a young guy once upon a time who cultivated elderly widows. He assumed that these other guys' mothers would enrich him, if he played them right. At the expense of the legitimate heirs.
Unless Mary has been magically transformed into a prayer-hearing goddess, the mother/son/stepson relationships have already fulfilled their purposes, already played out. Since my mother is still alive, this story is still being written.